This invention relates to an emergency exit door lock system, and more particularly this invention relates to an emergency exit door lock system wherein the system includes structure for delaying transition of the lock from a locked to unlocked mode so as to permit sounding of an alarm to give notice that the emergency exit door is being opened without authorization.
As explained in the aforecited co-pending U.S. Patent Applications, there is a need for a new type of emergency exit door lock in which opening of the lock is delayed. In the related patent applications this delay is accomplished by throttling a fluid. In order to reduce the cost of delayed action emergency exit door locks, another approach to the problem may be desirable in order to get this type of lock into wide use.
As indicated in the related patent applications, there is an inherent conflict between safety and security, even though these two concerns are interrelated. This conflict becomes readily apparent when one considers the problems encountered in trying to optimize the design of emergency exit doors. At least some doors in public buildings, such as schools, theaters, auditoriums, restaurants and the like must, by law, be equipped with latches or locks which can be readily opened from within the building should there be a fire or other emergency situation. These locks and latches pose a security problem since doors which can be readily opened from the inside of a building allow people within the buildings to easily escape with stolen articles and allow people within the buildings to open the doors and admit anyone they wish into the buildings. In the minds of security personnel, in many instances the security problems caused by easily openable emergency doors far outweigh the dangers of fire. Consequently, emergency exit doors are frequently locked with chains or other devices. This is probably done because security problems arise with greater frequency than fires and must be dealt with on a day-to-day basis, whereas fires occur infrequently and the dangers of fire are therefore ignored. If emergency exits are locked the results are often catastrophic when fires do occur and this causes fire departments great concern.